Highly Stretchable and Kirigami-Structured Strain Sensors with Long Silver Nanowires of High Aspect Ratio

Stretchable, skin-interfaced, and wearable strain sensors have risen in recent years due to their wide-ranging potential applications in health-monitoring devices, human motion detection, and soft robots. High aspect ratio (AR) silver nanowires (AgNWs) have shown great potential in the flexible and stretchable strain sensors due to the high conductivity and flexibility of AgNW conductive networks. Hence, this work aims to fabricate highly stretchable, sensitive, and linear kirigami strain sensors with high AR AgNWs. The AgNW synthesis parameters and process windows have been identified by Taguchi’s design of experiment and analysis. Long AgNWs with a high AR of 1556 have been grown at optimized synthesis parameters using the one-pot modified polyol method. Kirigami sensors were fabricated via full encapsulation of AgNWs with Ecoflex silicon rubber. Kirigami-patterned strain sensors with long AgNWs show high stretchability, moderate sensitivity, excellent linearity (R2 = 0.99) up to 70% strain and can promptly detect finger movement without obvious hysteresis.

Structure and Optical Property of Gold Nanoparticles Synthesized by Modified Polyol Method

In this research, Au nanoparticles were successfully synthesized by modified polyol method with commercial precursors to be gold (III) chloride trihydrate (HAuCl4·3H2O), ethylene glycol (EG), poly(vinylpyrrolidone) (PVP), sodium borohydride (NaBH4). The structure and properties of as-prepared Au nanoparticles have been investigated by X ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis-NIR spectroscopy. As a result, Au nanoparticles with the average particle size of 28.80 nm were successfully synthesized in the range of about 50 nm. It is evidenced that the assembly of gold nanoparticles was presented in their nucleation, growth, and formation.

Ni-, Co- and Pt-based nanocatalysts for hydrogen generation via hydrolysis of NaBH4

Ni-, Co- and Pt-based nanostructures were prepared via different physical-chemical methods and tested as the catalysts of hydrolysis of NaBH4. Ni-Co bimetallic nanoparticles with different Ni-Co ratios were synthesized by the modified polyol method via the reduction of in situ precipitated slurries of Ni and Co hydroxides by hydrazine in ethylene glycol solutions. It was found that a Ni- Co nanoparticles with the equal Ni/Co content and mean size of 130 nm are a more active catalyst as compared to Ni75Co25 and Ni25Co75 nanopowders and provide a constant rate of hydrogen evolution up to the full conversion of NaBH4. Zeolite supported Ni- and Co-based nanostructures (Ni-Z and Co-Z) as a convenient in use alternative to the metallic nanoparticles were synthesized via two-stage procedure consisted of adsorption of Ni2+ or Co2+ ions by zeolite from the aqueous solutions followed by the reduction of the adsorbed cations by NaBH4. Using SEM and EDX it was found that such method of synthesis provide the uniform distribution of 50 – 100 nm metallic nanopaticles both on the surface and in the bulk of the carrier due to the high cation-exchange capacity of the aluminosilicates. It was found that Co-Z catalyst is more active compared to Ni-Z and in studied conditions provides the H2 evolution rate close to 1450 mL/min per 1 g of precipitated metal. Various Pt-based nanocomposites were obtained by polyol synthesis and subsequently deposited on the carriers (carbon cloth or cordierite) as well as via a platinum electrodeposition on the titanium crump. It was found that the most efficient catalyst of the hydrolysis of NaBH4 is a cordierite-supported nanodispersed Pt which is able to maintain operation of a 30 W battery of fuel cells for 9-10 hours when using for the hydrolysis 1.1 L of 10 % NaBH4 solution.

Synthesis of Tungsten-Doped Vanadium Dioxide Using a Modified Polyol Method Involving 1-Dodecanol

The doping of tungsten into VO2 (M) via a polyol process that is based on oligomerization of ammonium metavanadate and ethylene glycol (EG) to synthesize a vanadyl ethylene glycolate (VEG) followed by postcalcination was carried out by simply adding 1-dodecanol and the tungsten source tungstenoxytetrachloride (WOCl4). Tungsten-doped VEGs (W-VEGs) and their calcinated compounds (WxVO2) were prepared with varying mixing ratios of EG to 1-dodecanol and WOCl4 concentrations. Characterizations of W-VEGs by powder X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and infrared and transmittance spectroscopy showed that tungsten elements were successfully doped into WxVO2, thereby decreasing the metal-insulator transition temperature from 68 down to 51 °C. Our results suggested that WOCl4 variously combined with 1-dodecanol might interrupt the linear growth of W-VEGs, but that such an interruption might be alleviated at the optimal 1:1 mixing ratio of EG to 1-dodecanol, resulting in the successful W doping. The difference in the solar modulations of a W0.0207VO2 dispersion measured at 20 and 70 °C was increased to 21.8% while that of a pure VO2 dispersion was 2.5%. It was suggested that WOCl4 coupled with both EG and 1-dodecanol at an optimal mixing ratio could improve the formation of W-VEG and WxVO2 and that the bulky dodecyl chains might act as defects to decrease crystallinity.

Rapid and Facile Synthesis of High-Performance Silver Nanowires by a Halide-Mediated, Modified Polyol Method for Transparent Conductive Films

Silver nanowires are receiving increasing attention as a kind of prospective transparent and conductive material. Here, we successfully synthesized high-performance silver nanowires with a significantly decreased reaction time by a modified polyol method. The synthesis process involved the addition of halides, including NaCl and NaBr, to control the release rate of Ag+ ions, as Cl− and Br− ions react with Ag+ ions to form AgCl and AgBr with different solubilities. As a result, Ag+ ions could be slowly released by graded dissolution, and the formation of silver nanowires was promoted. The results showed that the concentration of the added halides played an important role in the morphology of the final product. High-quality silver nanowires with an average diameter of 70 nm and average length of 21 μm were obtained by optimizing the reaction parameters. Afterwards, a simple silver nanowire coating was applied in order to fabricate the transparent conductive films. The film that was based on the silver nanowires provided a transmittance of 91.2% at the 550 nm light wavelength and a sheet resistance of about 78.5 Ω·sq−1, which is promising for applications in flexible and transparent optoelectronic devices.

Carbon Loaded Nano-Designed Spherically High Symmetric Lithium Iron Orthosilicate Cathode Materials for Lithium Secondary Batteries

In the present study, Li2FeSiO4 (LFS) cathode material has been prepared via a modified polyol method. The stabilizing nature of polyol solvent was greatly influenced to reduce the particle size (~50 nm) and for coating the carbon on the surface of the as-mentioned materials (~10 nm). As-prepared nano-sized Li2FeSiO4 material deliver initial discharge capacity of 186 mAh·g−1 at 1C with the coulombic efficiency of 99% and sustain up to 100 cycles with only 7 mAh·g−1 is the difference of discharge capacity from its 1st cycle to 100th cycle. The rate performance illustrates the discharge capacity 280 mAh·g−1 for lower C-rate (C/20) and 95 mAh·g−1 for higher C-rate (2C).

Synthesis and Characterization of Hydrophilic gama-Fe2O3 Nanoparticles for Biomedical Applications

The hydrophilic g-Fe2O3 nanoparticles coated with polyvinylpyrrolidone (PVP) were prepared in one step of the modified polyol method combined with an additional heat treating. The presence of maghemite (g-Fe2O3) phase was confirmed by using X-ray diffraction (XRD) and Raman Spectrometry on powder. FT-IR spectroscopy confirmed the presence of PVP on the nanoparticles surface and the Zeta potential also supported the coating of nanoparticles with a layer of PVP and a good stability in aqueous medium. SEM analysis showed that the prepared g-Fe2O3 nanoparticles have a spherical structural morphology with the tendency of agglomeration. Hysteresis loop shows a ferromagnetic behaviour at room temperature with a saturation magnetization up to 57 emu/g.

Synthesis, Characterization and CO Tolerance Evaluation in PEMFCs of Pt2RuMo Electrocatalysts

Pt2RuMo/C catalysts were synthesized by the modified polyol method in the presence and absence of Li(C2H5)3BH (LBH), annealed at 600 °C under H2 atmosphere to improve the reduction of Pt and Ru to provide stronger interactions between Mo and another metals. LBH affected the physico-chemical characteristics of Pt2RuMo, that is, in the presence of LBH an increment of Mo(IV) amount and a decrease in the PtRu alloying degree were observed. The catalytic activity for hydrogen oxidation in the presence and absence of CO (CO tolerance) of the Pt2RuMo/C catalysts as anodes in polymer electrolyte membrane fuel cells (PEMFCs) was compared to that of a commercial PtRu/C catalyst. The results indicated that the CO tolerance increased with an increase in Mo(IV) content, but the stability increased with an increment of the amount of Ru oxides in the catalysts.